Spinning, processing, and applications of carbon nanotube filaments, ribbons, and yarns

Abstract

Coagulation spinning produces structures such as fibers, ribbons, and yarns of carbon nanotubes. Stabilization, orientation, and shaping of spun materials are achieved by post-spinning processes. Advantages include the elimination of core-sheath effects due to carbonaceous contaminants, increasing mechanical properties, and eliminating dimensional instabilities in liquid electrolytes that previously prohibited the application of these spun materials in electrochemical devices. These advances enable the application of coagulation-spun carbon nanotube fibers, ribbons, and yarns in actuators, supercapacitors, and in devices for electrical energy harvesting.

Description

[0001] This application claims priority to application Ser. No. 09 / 946,432, filed Sep. 4, 2001, the entire contents of which are hereby incorporated by reference. This application claims priority to provisional Application No. 60 / 245,161, filed Nov. 3, 2000, the entire contents of which are hereby incorporated by reference.[0003] Methods are described for spinning fibers, ribbons, and yarns comprised of carbon nanotubes; the stabilization, orientation, and shaping of spun materials by post-spinning processes; and the application of such materials made by spinning.DESCRIPTION OF RELATED ART[0004] Since the discovery of carbon nanotubes by lijima and coworkers (Nature 354, 56-58, (1991) and Nature 361, 603-605 (1993)) various types of carbon nanotubes (NTs) have been synthesized. A single-wall carbon nanotube (SWNT) consists of a single layer of graphite that has been wound into a seamless tube having a nanoscale diameter. A multi-wall carbon nanotube (MWNT), on the other hand, compri...

AI Technical Summary

Benefits of technology

[0020] A further advantage of this invention, in part, is that it enables the continuous, high-throughput spinning of structures such as fibers, ribbons, and yarn. Yet another advantage of this invention is that it improves the mechanical properties of spun materials by providing means to increase the draw ratio of materials produced by the CS approach.

Problems solved by technology

The problem has been that no methods are presently available for the manufacture of nanotube articles that have these needed characteristics.

This obstacle has so far hindered applications development.

The problem is that MWNTs and SWNTs are insoluble in ordinary aqueous solvents and do not form melts even at very high temperatures.

Unfortunately, the fibers made by the CS process are not useful in applications as electrodes immersed in liquid electrolytes because of a surprising shape memory effect.

Because of this structural instability of fibers made by the CS process, they are unusable for critically important applications that use liquid electrolytes, such as in supercapacitors and in electromechanical actuators.

Another drawback of the current CS process is that it has been successfully applied only for nanotube-containing samples that contain an enormous amount of carbonaceous impurities (about 50% by weight or more).

Practice of this CS process with purified nanotubes has been universally unsuccessful, which has suggested that the carbonaceous impurities might be playing an important role in the initial stage of the CS spinning process.

Because of the presence of these impurities, the as-spun carbon nanotubes fibers contain about 50 volume percent of carbonaceous impurities, which degrade mechanical and electronic properties.

In addition, since the CS process does not enable a substantial mechanical draw, the obtained modulus of the fibers made this process is 15 GPa or less, which is over an order of magnitude lower than that of the constituent nanotubes (about 640 GPa).

As has been shown, the coagulation spinning (CS) process of the conventional art has disadvantages which prevent the utilization of carbon nanotube structures as electrode materials.

The conventional art process could not be successfully applied to carbon nanotubes that are substantially free of carbonaceous impurities.

The conventional art process was unstable since it could be practiced only in a narrow range of spinning parameters and a very restricted concentration range for the carbon nanotubes in the spinning solution.

Also, the nanotube fibers spun by the conventional art are not dimensionally stable and the mechanical properties degrade when these fibers are placed in liquid electrolytes for electrochemical applications.

Two critical deficiencies are (1) the need to conduct CS spinning with highly impure material that typically contains over 50% by weight carbonaceous impurities that are intimately mixed with the carbon nanotubes and (2) the dimensional and mechanical instability of materials spun by the CS method in the liquid electrolytes that are used for important applications.

The liquid jet containing chemically purified carbon nanotubes either broke into short segments during injection of the liquid jet into the carrier liquid or formed poorly structured ribbons that were too weak to remove from the wash bath.

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